Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations cover the safety profile (mutable, non-destructive, non-idempotent, closed-world), and the description adds value beyond them: the cost of $0.01 per call with no charge on failure, the observable effect of pausing (visitors see a page saying so), and that only supplied fields change. That is strong, but it doesn't mention what the call returns or whether re-sending identical input is safe to retry.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences: the first front-loads the operations, the second carries the partial-update rule and the pricing caveat. No filler and nothing buried mid-sentence.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With four flat parameters, no output schema, and annotations supplying the safety hints, the description gives an agent enough to call it correctly: what each field changes, that omitted fields remain untouched, and the cost. It stops short of stating return behavior, which is the only remaining gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Only 25% of the schema is documented (the code field), so the description has to compensate, and it does: 'send somewhere else' establishes url's meaning, 'retitle' establishes title, and the explanation of what a paused link shows gives paused real semantic weight. It still doesn't state the url format/constraints or that code is the required identifier.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description names the concrete mutations ('send somewhere else', 'retitle', 'pause/resume') that map onto the parameters, so an agent knows exactly what this changes on a short link. It doesn't explicitly distinguish itself from the links_shorten / links_delete / links_get siblings, so a 4 rather than a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

'Give only what changes' is a genuine usage instruction for a partial update, and the pause semantics clarify the toggle. However, it never says when to use this versus links_shorten (create) or links_delete, nor does it exclude anything, leaving the routing to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.